Normally a wind turbine comprises a plurality of blades connected to a nacelle through a rotor hub. The wind turbine further includes a control mechanism to control the pitch of the blades. The wind turbines adjust rotor blade pitch for several reasons. The blades are pitched to improve the wind turbine efficiency by adapting the blade aerodynamics with wind speed changes. Another reason is to take the blades to an unloaded or feathered condition, in the event that wind speed exceeds the maximum safe rated speed or in the event of fault conditions. Wind turbines typically include a mechanism for axially pivoting the plurality of blades relative to the rotor hub to shift the blade between different pitch angles. To perform the pitch, each blade is provided with a pitch bearing between the hub and the blade, and some sort of mechanism, most often a hydraulic cylinder, to provide the force for pitching the blade and maintaining it in a given position. This pitching arrangement enables each blade to be turned approximately 120° around their rotational axis.
In the existing arrangement, the inner/outer bearing rings are manufactured in such a way that only a portion of the ring includes gears. This kind of arrangement is sufficient to rotate the blade for the required pitch angle. Though, for this type of bearing rings, it is very hard to manufacture the pattern of gears on the inner/outer ring. The other problem is that even after manufacturing the gears, when the gear teeth are hardened, there are chances of distortion at the end of the geared portion. So, homogeneous hardening cannot be done. Also, it is always difficult to remove the complete bearing ring for maintenance or repair purpose.
While various other methods have been developed in the past for providing an arrangement to maintain the pitching arrangement in the wind turbines, there is still room for development. Thus a need persists for further contributions in this area of technology.